1. Field of the Invention
This invention relates generally to the shielding of a disk during thin film coating, and more particularly to using discrete releasably connected shields.
2. Description of the Prior Art
Media disks are coated by a thin film coater, which is well known in the art. An example of a suitable coater is the Unaxis Big Sprinter Coater manufactured by Unaxis located at Balzers, Liechtenstein. The thin film coater has an automated disk loader mechanism. This disk loader mechanism has a double ended transfer arm that transfers a single disk with a metal ID and OD mask from the vacuum coater to a position where the thin film coated disk can be picked from the ID and OD mask and replaced with an uncoated disk. The removal of the thin film coated disk from this position and replacement of it with a not thin film coated disk can be done by human hand, but is typically done by external automated disk handling equipment that is not part of the disk coater. On each thin film machine cycle, the thin film coated disk is replaced with an uncoated disk. The ID and OD metallic masks are not replaced until the thin film coatings have built up to an extent that they begin to flake from the metallic mask or the extent that the ID mask has increased in size or the OD mask opening has decreased in size as to not allow thin films to coat an adequate surface area of the disk. At this point, the ID and OD masks with thin film coating build up are replaced with masks that have had the thin film coating removed. The ID mask covers part of the ID surface area and the disk ID center hole thereby preventing sputtering material from going through the disk ID center hole and building up thin film coating on the carrier. The 120 mm disks are typically coated and masked on only one side.
It is no longer necessary or desirable to always have disks of 120 mm in diameter. New technology has become available which is able to utilize a disk of 32 mm in diameter. Since these are substantially smaller, multiples of the small disks are coated at once. Six small disks may be placed in a disk tray. The disk tray is used to hold the smaller disks and mask the outer diameter of the smaller disk. On these small disks, it is not necessary or preferred to mask the ID surface area of the disks. No center masks are used to prevent sputtered material from going through the disk ID center hole and building up on the carrier. A prior art carrier is shown in FIG. 6. The carrier 100 is a carrier of the type used in a thin film coater such as a Unaxis coater. The carrier 100 has a base plate 101. On top of base plate 101 is mounted a ring shaped shield 102. The shield 102 is secured to the base plate 101 by three screws 103. The central portion of the ring 103 is positioned so that it is directly in alignment with the center hole of the disks to be coated. The shield 102 is positioned in a recess in the base plate 101, so that the top surface of the shield 102 is at the same elevation as the top surface of the base plate 101. Magnets 104 are positioned and secured in the base plate 101 and are used to secure the disk tray to the carrier 100. Mounting holes 105 and 106 are provided to mount the carrier 100 to the coater (not shown). Therefore, the sputtering that goes through the center opening of the disk causes a spray pattern, in theory, to land on the shield 102. However, the shield 102 is typically not wide enough and the circular spray pattern will extend on to the base plate 101. Further, when the sputtering builds up sufficiently to require that the shield 102 be replaced, it is necessary that the screws 103 be removed. Still further, when in the coater, any disk tray would have to be removed to allow access to the screws 103 to remove the shield 102.
In one embodiment, the invention is a carrier for use in thin film coating of disks. The disks are held in a disk tray. The disks have a center opening through which the thin film coating can go through. The carrier includes a base plate for receiving the disk tray. A plurality of discrete shields are releasably connected to the base plate. The shields are positioned in alignment with the center opening of the disks.
In another embodiment, the invention is a carrier and disk tray combination. The disk tray is for holding a plurality of disks for thin film coating. The disks have a center opening. The combination includes a disk tray having a plurality of openings for receiving the disks. A carrier is provided for holding the disk tray during coating. A plurality of discrete shields are releasably connected to the carrier. The shields are positioned in alignment with the center openings of the disks, wherein a spray pattern of sputtering during coating is received on the shields.
In another embodiment, the invention is a carrier and disk tray combination, the disk tray holds a plurality of disks for thin film coating. The disks have a center opening. The combination includes a disk tray having a plurality of openings for receiving the disks. A carrier is provided for holding the disk tray during coating. A plurality of discrete shields are releasably connected to the carrier, the shields are positioned in alignment with the center openings of the disks, wherein a spray pattern of sputtering during the coating is received on the shields. The shields are sized less than the openings in the disk tray, wherein the shields are replaceable when the carrier and disk tray combination is assembled.
In another embodiment, the invention is a method of replacing shields on a carrier of a thin film coater. The carrier holds a disk tray during coating. The disk tray has a plurality of openings to hold a plurality of disks, each disk having a central opening. The method includes releasably connecting a plurality of shields to the carrier, the shields in alignment with the central openings of the disk. The disk tray is loaded, with the disks, onto the carrier. The disks are coated and the shields collect the coating going through the central openings. A disk tray is loaded, without disks, onto the carrier. The carrier and disk tray is moved into the coater. Then, one reaches in through the opening of the disk tray and removes the shields and replaces the plurality of shields with coating with a plurality of shields with no coating and releasably connects the second plurality of shields to the carrier.